The present invention relates to apparatus for separating particulate material, such as tobacco shreds, from a gaseous carrier medium. More particularly, the invention relates to improvements in apparatus of the type known as air locks wherein a cell wheel rotates in a housing to move successive cells past the discharge end of a conduit for a mixture of particulate material and carrier medium, wherein the carrier medium is withdrawn by a suction pipe, and wherein the particulate material leaves the housing through a discrete outlet. Such apparatus are normally utilized to admit particles of tobacco into the magazine of a machine for the processing of tobacco. The magazine receives particles of tobacco from a remote source by way of a pneumatic conduit wherein the particles are transported in a stream of air or another suitable gaseous carrier medium. Sieves are disposed between the intake end of the suction pipe and the cells of the rotating wheel to intercept the particles of tobacco while permitting the carrier medium to flow into the suction pipe. Typical examples of machines whose magazines receive tobacco by way of the above outlined apparatus are cigarette makers wherein the magazine supplies particles of shredded or otherwise comminuted tobacco to a distributor which converts the particles into a shower and thereupon into a narrow stream ready to be equalized and draped into a web of cigarette paper or other suitable wrapping material. The resulting continuous cigarette rod is subdivided into plain cigarettes of desired length.
As a rule, the air lock is disposed directly above the magazine of a maker of cigarettes, cigars or cigarillos. It is desirable to ensure complete separation of tobacco particles from the gaseous carrier medium. This is necessary in order to enable the maker to form a continuous rod-like tobacco filler of predictable consistency.
British Pat. No. 335,259 discloses an air lock wherein a housing confines a rotary cell wheel as well as a rotary drum-shaped sieve. The sieve segregates the carrier medium from tobacco particles, and the cell wheel removes the particles from the housing. The sieve is disposed above the cell wheel; therefore, the housings of such air locks are rather bulky and the air locks must be provided with means for rotating the cell wheel as well as with means for transmitting torque to the rotary sieve.